Many mobile devices, such as cellular phones or smartphones, have multiple microphones to receive sound waves from speech for example, and to generate audio. Multiple microphones may be used in order to provide spatial audio affects and/or for better quality noise blocking on mobile phones for example. Each microphone is considered its own channel forming its own signal which is combined with other signals to form a single mixed output signal to listen to the sounds on the same device or another audio device receiving the output signal. It is also possible to generate multiple mixed output signals as intermediate signals for purposes of speech or audio enhancement and processing. These systems may provide a number of available alternative output signal combinations to provide different effects or different levels of quality of the signal. The multichannel systems are often processed by using a switch matrix which have high computational costs, especially when performing multiplication. Conventional solutions use tree-based approaches to limit the multiplication operations, but the tree becomes more complex and computationally costly with each branch added. Thus, these tree-based systems are often limited to just a small subset of all possible signal combinations that could be available. Therefore, a signal mixing method and system that provides many different signal combinations with a low computational cost is desired.